What type of lamps are you using, brand and color temperature?
pm.

Lights may be too bright. More likely they are just overheating the leaves and causing dessication. Or perhaps they are too dry. Run a fan, or lift the lights a little, make sure they are watered. Also check that the temperature drops at least 10F at night.

I think Shrubs is right, some of my herbs were doing the same, and putting the light down a little seems to have helped. pm.

I don't get it
shrubs says "lift the lights a little"
object16 says "putting the light down a little seems to have helped"

Which is it, lift the lights, or put them down?
Dave